The present invention relates to a device for the pneumatic inspection of smoking items, in particular cigarettes.
Along cigarette packaging and conditioning lines, in particular in filter tip attachment machines, devices are installed which can carry out pneumatic inspections on the cigarettes, both to check the correct degree of ventilation for so-called ventilated cigarettes, which have ventilation holes, normally made using laser ray devices, and to check that the cigarettes have been assembled correctly and their component parts are in good condition.
Known inspection devices of this type normally comprise a conveyor, usually consisting of a rotary drum with a succession of radial seats designed to receive and hold cigarettes by suction. The drum normally operates in conjunction with and is integral with a plurality of pneumatic circuits whose ends are located at the ends of each cigarette and are designed so that, during rotation of the drum and at a pneumatic inspection station, they make contact and form a seal with the ends of the cigarettes, which are in this way inserted in the pneumatic circuits. The pneumatic circuits are supported by two disks positioned on opposite sides of the drum and coaxial with it. At the inspection station the infeeds are connected to a source of inspection fluid, whilst the outfeeds are connected to a pneumaticxe2x80x94electric transducer which is outside and fixed relative to the drum and the disks. The transducer can transform the pressure value detected into a corresponding electrical signal, which is processed in such a way as to check the correct degree of ventilation and/or correct cigarette assembly.
The connection between the rotary pneumatic circuits and the fixed transducer is obtained using a graphite pad with a passage for the inspection fluid which allows the connection to be made without drops in the pressure. However, it has been found that the pad tends to wear in relatively short periods, causing a loss of seal and, during wear produces residual powders which tend to dirty the inspection fluid passage, making the processing system response unreliable.
There are also known pneumatic inspection devices comprising, at the inspection station, and alongside the outer surface of the drum, a suction hood with a first portion which is smaller than the longitudinal dimensions of the cigarettes and a second portion which is substantially the same size as the longitudinal dimensions of the cigarettes. In this way, the inside of the hood, at each seat which passes through its portions, creates two different and successive ambient conditions. As a result, a first measurement is taken by subjecting each cigarette to a given pressure, with the exception of its end, which is left at atmospheric pressure, and a second measurement is taken by subjecting the entire cigarette to a given pressure. The ratio between these two measurements, compared with a preset value, leads to the processing of a signal which indicates the condition of the cigarettes and controls a device which rejects any faulty cigarettes.
This device has proved unreliable at high speeds due to the relatively lengthy periods required by the hood to create the two different ambient conditions inside it. Moreover, if said ambient conditions are upset by the absence of a cigarette inside a seat, the hood has proved itself unable to re-establish the balanced ambient conditions in relatively short periods.
The aim of the present invention is to overcome the above-mentioned disadvantages.
Accordingly, the present invention provides a device for the pneumatic inspection of smoking items, comprising a conveyor which has a plurality of seats, each designed to receive an item, and pneumatic fluid generator means which can be connected to said seats at an inspection station, so as to subject the item to the action of the fluid, and wherein each seat is connected to a pressure transducer which issues at least one signal depending on the action of the fluid and which indicates the condition of the smoking item.